1. Field of the Invention
The present invention relates to a push button switch used for an elevator switch and the like.
2. Description of the Related Art
FIGS. 33 and 34 show a conventional push button switch. The push button switch S-1 has a case 90 and a setting portion 100 is set to the case 90. Moreover, two fixed terminals 91 are set to the backs of opposite side faces of the case 90 and these fixed terminals 91 respectively have a fixed contact point at their upper faces.
Furthermore, an operating shaft 92 is movably set to the case 90, and a movable piece 93 is set to the inner end of the operating shaft 92 so that the fixed terminals 91 are faced each other and has a movable contact point 93a opposite to the fixed contact point 91a. Furthermore, a diffusion plate 95, character plate 94, and key top 96 are set to the outer end of the operating shaft 92 so that they are overlapped each other.
Furthermore, the operating shaft 92 is raised by a return spring 97 and the movable contact point 93a separates from the fixed contact point 91a. 
A lamp 98 is set to a lamp holder 99. Then, by setting the case 90 to a setting destination member (not illustrated) while housing the lamp 98 and lamp holder 99 in the case 90, the push button switch S-1 is constituted. The push button switch S-1 uses a directly-under illumination system in which the lamp 98 is set directly under a push button portion constituted by the diffusion plate 95, character plate 94, and key top 96.
Moreover, by pushing in the key top 96 of the push button portion by a finger and thereby, pushing in the operating shaft 92 against the return spring member 97, the movable contact point 93a of the movable piece 93 contacts wit the fixed contact point 91a of the fixed terminal 91, the contact point closes, and the switch is turned on.
When the lamp 98 lights up, it illuminates the diffusion plate 95 from its back. Therefore, characters on the character plate 94 can be seen from the outside of the key top 96 by the light passing through the diffusion plate 95.
However, because the above conventional push button switch S-1 is constituted so as to push the key top 96, directly move the movable contact point 93a, close the contact point portion constituted by the movable contact point 93a and fixed contact point 91a, and turn on the switch. Therefore, the key top 96 requires a movement stroke equal to or more than a contact point gap necessary to open or close the contact point of the contact point portion, that is, the opening distance between the contact points 91a and 93 for the contact point portion to be safely turned off. Thus, there is a problem that the whole switch becomes thick.